BETHESDA, Md. - The search for a missing 12-year-old boy in Montgomery County had a happy ending as he was found safe overnight and returned to his family.

It was a mother's worst nightmare. Dominique Stevens said her 12-year-old son, Nathaniel Castro, had an argument with his sister, so she told him to take his bicycle out around the neighborhood to let off some steam.

It was around 4 p.m. Thursday, but when two hours went by and he didn't return, panic started to set in.

“It was my worst nightmare and something I wouldn’t wish on anybody,” Stevens said. “It’s just a feeling like the bottom has dropped out from beneath you.”

She then called police to report her son was missing. Montgomery County police and U.S. Park Police responded by searching with helicopters and K-9 units.

A group of volunteers gathered at nearby Bannockburn Elementary School and fanned out to search.

But it turns out Castro had hopped on his bike, rode through the neighborhood and then kept going and going all the way to D.C. He had traveled a total distance of eight miles.

He hit MacArthur Boulevard and took it to Foxhall Road. He then rode along M Street into Georgetown, continued to the West End neighborhood and finally came to a stop at New Hampshire Avenue.

Castro stopped because he got a flat tire. With no cell phone, he decided to start walking. It was so cold that he took off his socks and used them to warm his hands.

A volunteer eventually found the boy walking along MacArthur Boulevard at 1 a.m.

Stevens said he was cold, hungry and tired. She is shocked at how far he traveled, but her 12-year-old made it home safe and unharmed.

“I’m really grateful to everybody who was involved in searching for him and reaching out to us,” said Stevens. “I don’t know how I can thank them enough.”

Montgomery County police said they are also thankful for all of the residents who called in possible sightings and the community members who came out to help.